On Fri, 2023-05-05 at 16:17 +0200, Thomas Hellström wrote:
> Allow drivers to resolve a WW transaction rollback. This allows for
> 1) Putting a lower-priority transaction to sleep allowing another to
> succeed instead both fighting using trylocks.
> 2) Letting the driver know whether a received -ENOMEM is the result
> of
> competition with another WW transaction, which can be resolved using
> rollback and retry or a real -ENOMEM which should be propagated back
> to user-space as a failure.
>
> Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Christian, Any objections?
/Thomas
> ---
> drivers/gpu/drm/ttm/ttm_bo.c | 17 +++++++++++++++--
> include/drm/ttm/ttm_bo.h | 2 ++
> 2 files changed, 17 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c
> b/drivers/gpu/drm/ttm/ttm_bo.c
> index bd5dae4d1624..c3ccbea2be3e 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -561,6 +561,10 @@ static int ttm_mem_evict_wait_busy(struct
> ttm_buffer_object *busy_bo,
> if (!busy_bo || !ticket)
> return -EBUSY;
>
> + /* We want to resolve contention before trying to lock again.
> */
> + if (ctx->propagate_edeadlk && ctx->contended_bo)
> + return -EDEADLK;
> +
> if (ctx->interruptible)
> r = dma_resv_lock_interruptible(busy_bo->base.resv,
> ticket);
> @@ -575,7 +579,15 @@ static int ttm_mem_evict_wait_busy(struct
> ttm_buffer_object *busy_bo,
> if (!r)
> dma_resv_unlock(busy_bo->base.resv);
>
> - return r == -EDEADLK ? -EBUSY : r;
> + if (r == -EDEADLK) {
> + if (ctx->propagate_edeadlk) {
> + ttm_bo_get(busy_bo);
> + ctx->contended_bo = busy_bo;
> + }
> + r = -EBUSY;
> + }
> +
> + return r;
> }
>
> int ttm_mem_evict_first(struct ttm_device *bdev,
> @@ -816,7 +828,7 @@ int ttm_bo_mem_space(struct ttm_buffer_object
> *bo,
> goto error;
> }
>
> - ret = -ENOMEM;
> + ret = (ctx->propagate_edeadlk && ctx->contended_bo) ? -
> EDEADLK : -ENOMEM;
> if (!type_found) {
> pr_err(TTM_PFX "No compatible memory type found\n");
> ret = -EINVAL;
> @@ -913,6 +925,7 @@ int ttm_bo_validate(struct ttm_buffer_object *bo,
> if (ret)
> return ret;
> }
> +
> return 0;
> }
> EXPORT_SYMBOL(ttm_bo_validate);
> diff --git a/include/drm/ttm/ttm_bo.h b/include/drm/ttm/ttm_bo.h
> index 8b113c384236..d8e35a794ce5 100644
> --- a/include/drm/ttm/ttm_bo.h
> +++ b/include/drm/ttm/ttm_bo.h
> @@ -181,8 +181,10 @@ struct ttm_operation_ctx {
> bool gfp_retry_mayfail;
> bool allow_res_evict;
> bool force_alloc;
> + bool propagate_edeadlk;
> struct dma_resv *resv;
> uint64_t bytes_moved;
> + struct ttm_buffer_object *contended_bo;
> };
>
> /**
